ABSTRACT
Cutting fluids represent a significant portion of total manufacturing costs. In some processes the initial investment and maintenance costs for the cutting fluids can account for up to 15-17% of the total manufacturing costs and close to half of the machine tool costs [1,2]. Cutting fluids also play a vital role in lubricating and removing heat as well as swarf from a process. Hence the proper selection and application of cutting fluids is a major economic as well as engineering issue for high performance machining. The application of coolants and lubricants is obviously one of the most affordable and beneficial ways to improve machining performance. The successful application of coolants and lubricants can often result in cutting tool life improvements on the order of 1.2-4 times, intensification of cutting parameters by 20-60%, and productivity increases of 10-50%. The majority of the coolants and lubricants that are used in practice today are fluids. It is well known from the practice of machining that a flood of liquid is directed over the tool to act as a coolant or lubricant, or both. Some typical objectives and properties of these fluids follow:
• To prevent overheating of the machine, tool, and workpiece during cutting (cooling effect) • To reduce friction and the amount of heat generation; this results in tool life and surface finish
improvements (lubricating effect) • To reduce the seizure and galling phenomena (antifriction properties) • To clear chips from the cutting zone (flushing effect)
GEORGE: “2095_c012” — 2006/2/27 — 17:27 — page 2 — #2
• To enhance fluid penetration to the cutting zone (good wetting properties) • To provide a degree of corrosion protection • To allow chips and other metal debris to settle out (low viscosity) • Resistance to the formation of a sticky or gummy residue on parts as well as on machine tools • Chemical stability to provide a safe work environment • Antibacterial properties • Overall economical efficiency
Application of efficient coolants and lubricants results in a better surface finish for final machined components, especially during machining of hard to machine alloys. These alloys are becoming increasingly topical for the North American market. A large variety of cutting fluids are currently available on the market. These fluids all try to improve cutting performance on one hand while meeting numerous requirements such as those outlined above on the other. The proper selection and development of advanced fluids are possible based on an in-depth understanding of the mechanism associated with the interaction between the tool and the workpiece material during cutting. However, at this time the selection of fluids depends mainly on extensive testing and practical experience. The fundamentals of a fluid’s impact on friction in general are based on well-known tribological studies [3-10]. The result of these studies for a machining application leads to the wide use of surface active materials in cutting fluids.
